The first objective is to use multi-color fluorescence in situ hybridization (M-FISH) to link the zebrafish genetic map to specific chromosomes. At least four markers from each genetic linkage group will be mapped to specific zebrafish chromosomes. These will be labeled in different colors so a "bar code" for each chromosome pair will be produced. The second objective is to prepare "paint probes" for each zebrafish chromosome by microdissection and amplification of chromosomes from a diploid and or haploid cell line. The probes will be used to characterize standard mutant lines produced by gamma-irradiation which contain deletion or chromosome rearrangements. This research represents a first step in linking the information being generated by the on-going large scale genomic mapping efforts in several zebrafish laboratories with state-of-the-art cytogenetic analyses of the chromosomes. Including cytogenetics in the genomic effort is important for several reasons. First, it is an independent check on syntenic relationships obtained with the other mapping techniques and will be especially useful for ordering markers adjacent to centromeres and telomeres. Second, it will provide "paint probes" for zebrafish chromosomes which would be useful in checking radiation hybrids, in deletion mapping, and in isolation of chromosome-specific BACs. Third, the paint probes and mapping of specific BACs will help establish whether zebrafish retain extensive duplicated chromosomal regions as a result of an ancestral polyploidization event in fishes. In this case there will often be two groups of syntenic genes homologous to those conserved in mammals and birds. Cytogenetic mapping is a quick way to determine how many unlinked copies of a gene are present in a genome and to sort out which clones correspond to which loci. This would be very helpful in positional candidate cloning of zebrafish mutants.